βIII-tubulin distribution in the human olfactory bulb: effects of aging and sex

Background. Numerous studies link olfactory impairment to accelerated cognitive decline in neurodegenerative diseases, yet the mechanism by which the olfactory bulb participates in these processes remains unclear. βIII-tubulin is one of the most commonly used neuronal markers, but data on its distribution in the olfactory bulb are limited.

Aim. To analyze the distribution of βIII-tubulin in the olfactory bulbs of men and women during aging.

Methods. The study was performed on autopsy material. Olfactory bulbs were obtained from 10 men and 14 women of elderly (60–74 years, n = 11) and senile (75–89 years n = 13) ages. Histological sections were stained with hematoxylin and eosin, Nissl stain, and Mallory’s trichrome for cytoarchitectonic analysis. Immunohistochemical analysis was performed using primary antibodies against neuron-specific βIII-tubulin. Morphometric and statistical analyses were carried out.

Results. βIII-tubulin immunoreactivity was mainly detected in the olfactory nerve fiber layer and the glomerular layer. Analysis of sex differences revealed a significant (p = 0.006) predominance of the βIII-tubulin reaction area in olfactory bulb sections obtained from women. This aligns with research findings showing that women have nearly twice as many neurons in their olfactory bulbs and typically exhibit better odor identification ability compared to men. Despite a trend towards a decrease in βIII-tubulin levels with age, no statistically significant differences were found.

Conclusion. The study revealed sexand age-related variability in the distribution of βIII-tubulin in the human olfactory bulb. Therefore, these factors should be taken into account when performing functional olfactory diagnostics.

1. Dan X, Wechter N, Gray S, Mohanty JG, Croteau DL, Bohr VA. Olfactory dysfunction in aging and neurodegenerative diseases. Ageing Res Rev. 2021; 70: 101416. doi: 10.1016/j.arr.2021.101416

2. Doty RL. Olfactory dysfunction in neurodegenerative diseases: is there a common pathological substrate? The Lancet Neurology. 2017; 16(6): 478–488. doi: 10.1016/s1474-4422(17)30123-0

3. Morozova SV, Savvateeva DM. Olfactory disorders in patients with neurodegenerative and mental diseases. Russian Medical Journal. 2014; 9: 673 (In Russ.).

4. Mak E, Fought AJ, Wiste HJ, Przybelski SA, Reid RI, Schwarz CG, et al. Sex-Specific Associations of α-Synuclein Pathology with Tau Accumulation. JAMA Netw Open. 2026; 9(3): e260461. doi: 10.1001/jamanetworkopen.2026.0461

5. Kharlamova AS, Godovalova OS, Otlyga EG, Proshchina AE. Primary and secondary olfactory centres in human ontogeny. Neurosci Res. 2023; 190: 1–16. doi: 10.1016/j.neures.2022.12.005

6. Bhatnagar KP, Kennedy RC, Baron G, Greenberg RA. Number of mitral cells and the bulb volume in the aging human olfactory bulb: a quantitative morphological study. Anat Rec. 1987; 218(1): 73–87. doi: 10.1002/ar.1092180112

7. Meisami E, Mikhail L, Baim D, Bhatnagar KP. Human olfactory bulb: aging of glomeruli and mitral cells and a search for the accessory olfactory bulb. Ann N Y Acad Sci. 1998; 855: 708–715. doi: 10.1111/j.1749-6632.1998.tb10649.x

8. Sama-ul-Haq, Tahir M, Lone KP. Age and gender-related differences in mitral cells of olfactory bulb. J Coll Physicians Surg Pak. 2008; 18(11): 669–673.

9. Kovács T. Mechanisms of olfactory dysfunction in aging and neurodegenerative disorders. Ageing Res Rev. 2004; 3(2): 215–232. doi: 10.1016/j.arr.2003.10.003

10. Son G, Jahanshahi A, Yoo SJ, Boonstra JT, Hopkins DA, Steinbusch HWM, et al. Olfactory neuropathology in Alzheimer’s disease: a sign of ongoing neurodegeneration. BMB Rep. 2021; 54(6): 295–304. doi: 10.5483/BMBRep.2021.54.6.055

11. Shoff TA, Derbez-Morin M, Cai P, Julian RR. The microtubule nexus linking amyloid beta and tau: A simple and unifying theory for the underlying cause of Alzheimer’s disease. PNAS Nexus. 2026; 5(3): pgag034. doi: 10.1093/pnasnexus/pgag034

12. Lee VM, Pixley SK. Age and differentiation-related differences in neuron-specific tubulin immunostaining of olfactory sensory neurons. Brain Res Dev Brain Res. 1994; 83(2): 209–215. doi: 10.1016/0165-3806(94)00139-1

13. Santiago-Mujika E, Luthi-Carter R, Giorgini F, Mukaetova-Ladinska EB. Tubulin Isotypes and Posttranslational Modifications in Vascular Dementia and Alzheimer’s disease. J Alzheimers Dis Rep. 2022; 6(1): 739–748. doi: 10.3233/ADR-220068

14. Lucas L, Tsoi PS, Quan MD, Choi KJ, Ferreon JC, Ferreon ACM. Tubulin transforms Tau and α-synuclein condensates from pathological to physiological. Nat Commun. 2026; 17(1): 3362. doi: 10.1038/s41467-026-69618-3

15. von Hungen K, Chin RC, Baxter CF. Brain tubulin microheterogeneity in the mouse during development and aging. J Neurochem. 1981; 37(2): 511–514. doi: 10.1111/j.1471-4159.1981.tb00485.x

16. Santiago-Mujika E, Luthi-Carter R, Giorgini F, Kalaria RN, Mukaetova-Ladinska EB. Tubulin and Tubulin Posttranslational Modifications in Alzheimer’s disease and Vascular Dementia. Front Aging Neurosci. 2021; 13: 730107. doi: 10.3389/fnagi.2021.730107

17. Bédard A, Parent A. Evidence of newly generated neurons in the human olfactory bulb. Brain Res Dev Brain Res. 2004; 151(1–2): 159–168. doi: 10.1016/j.devbrainres.2004.03.021

18. Oliveira-Pinto AV, Santos RM, Coutinho RA, Oliveira LM, Santos GB, Alho AT, et al. Sexual dimorphism in the human olfactory bulb: females have more neurons and glial cells than males. PLoS One. 2014; 9(11): e111733. doi: 10.1371/journal.pone.0111733

19. Durante MA, Kurtenbach S, Sargi ZB, Harbour JW, Choi R, Kurtenbach S, et al. Single-cell analysis of olfactory neurogenesis and differentiation in adult humans. Nat Neurosci. 2020; 23(3): 323–326. doi: 10.1038/s41593-020-0587-9

20. Kunkhyen T, Brechbill TR, Berg SPR, Pothuri P, Rangel AN, Gupta A, et al. Cell type- and layer-specific plasticity of olfactory bulb interneurons following olfactory sensory neuron ablation. Sci Rep. 2024; 14(1): 17771. doi: 10.1038/s41598-024-68649-4

21. Fitzek M, Patel PK, Solomon PD, Lin B, Hummel T, Schwob JE, et al. Integrated age-related immunohistological changes occur in human olfactory epithelium and olfactory bulb. J Comp Neurol. 2022; 530(12): 2154–2175. doi: 10.1002/cne.25325

22. Sorokowski P, Karwowski M, Misiak M, Marczak MK, Dziekan M, Hummel T, et al. Sex Differences in Human Olfaction: A Meta-Analysis. Front Psychol. 2019; 10: 242. doi: 10.3389/fpsyg.2019.00242

23. Flores-Cuadrado A, Saiz-Sanchez D, Mohedano-Moriano A, Lamas-Cenjor E, Leon-Olmo V, Martinez-Marcos A, et al. Astrogliosis and sexually dimorphic neurodegeneration and microgliosis in the olfactory bulb in Parkinson’s disease. NPJ Parkinsons Dis. 2021; 7(1): 11. doi: 10.1038/s41531-020-00154-7

24. Yeo BSY, Song HJJMD, Tan BKJ, Suresh A, Ho OTW, Chan JH, et al. Olfactory Impairment and Incident Cognitive Decline: A Systematic Review and Meta-Analysis. Int Forum Allergy Rhinol. 2025; 15(12): 1347–1358. doi: 10.1002/alr.23635

25. Liu Q, Chen B, Wang Q, Xu D, Yang M, Lin G, et al. Sex differences in the relationship between olfactory and cognitive impairment among subjects with subjective cognitive decline and mild cognitive impairment. Biol Sex Differ. 2025; 16(1): 12. doi: 10.1186/s13293-025-00691-x

26. Kamath V, Senjem ML, Spychalla AJ, Chen H, Palta P, Mosley TH, et al. The Neuroanatomic Correlates of Olfactory Identification Impairment in Healthy Older Adults and in Persons with Mild Cognitive Impairment. J Alzheimers Dis. 2022; 89(1): 233–245. doi: 10.3233/JAD-220228

27. Fatuzzo I, Niccolini GF, Zoccali F, Cavalcanti L, Bellizzi MG, Riccardi G, et al. Neurons, Nose, and Neurodegenerative Diseases: Olfactory Function and Cognitive Impairment. Int J Mol Sci. 2023; 24(3): 2117. doi: 10.3390/ijms24032117

28. Prem B, Liu DT, Boehme K, Maurer MT, Renner B, Mueller CA. Factors Associated with Persisting Olfactory Dysfunction After COVID-19. Clin Otolaryngol. 2025; 50(1): 53–61. doi: 10.1111/coa.14233

29. Knight JE, Yoneda T, Lewis NA, Muniz-Terrera G, Bennett DA, Piccinin AM. Transitions between Mild Cognitive Impairment, Dementia, and Mortality: The Importance of Olfaction. J Gerontol a Biol Sci Med Sci. 2023; 78(7): 1284– 1291. doi: 10.1093/gerona/glad001

30. Grillo F, Bruzzone M, Pigozzi S, Prosapio S, Migliora P, Fiocca R, et al. Immunohistochemistry on old archival paraffin blocks: is there an expiry date? J Clin Pathol. 2017; 70(11): 988–993. doi: 10.1136/jclinpath-2017-204387